Shot blasting chambers, storage chambers and the like



June 17, 1958 T. A. ARNOLD SHOT ELASTING CHAMBERS. STORAGE CHAMBERS AND THE LIKE Filed Sept. 15, 1954 2 Sheets-Sheet 1 720 A AMSON ARNOLD ATTORNEY June 17, 1958 T. A. ARNOLD 2,339,338

- SHOT BLASTING CHAMBERS. STORAGE CHAMBERS AND THE LIKE Filed Sept. 15. 1954 2 Sheets-Sheet 2 //V VE N TOR 7750 ADAMSO/V ARNOLD SHOT BLASTIN CHAMBERS, STORAGE CHAMBERS AND THE LIKE Ted Adamson Arnold, Mitcham, Victoria, Australia, as signor to William H. Mead, Oakland, Calif.

Application September 15, 1954, Serial No. 456,257 8 Claims. c1. 302-36) Shot blasting chambers as now constructed have a grilletype floor and the walls of the chamber extend downwardly below the floor and converge inwardly to form one-or more collecting hoppers for the spent abrasive, dust and debris which then passes through discharge openings and is suitably conveyed to a storage hopper.

Thus the chamber is formed with a hopper-like extension below the floor and as the angle of slope of the sides of the hopper must exceed the angle of repose of the abrasive, the hoppers are necessarily relatively deep. More particularly, the sides of the hopper are usually arranged at an angle of about 45 to the horizontal plane, in which case the depth of the hopper is approximately equal to one half of the width of the chamber.

Consequently, when as is usual, the grille floor is ar ranged at or about ground lever, the collecting hopper is necessarily arranged below that level and the large excavation required for this purpose adds considerably to the cost of the structure and sometimes introduces serious drainage problems.

An alternative procedure is to arrange the hopper wholly or partly above ground level but this requires much greater headroom which is not always available, apart from which the grille floor is then necessarily disposed substantially above ground level, so that it is necessary to construct ramps or to provide hoisting means for the Work pieces to be treated.

Similarly storage chambers or silos, for powdered or other particulate material, such as cereal grains, converge towards their lower ends at an angle exceeding the angle of repose of the material, so that the storage capacity is necessarily considerably reduced.

An object of this invention is to provide a chamber of the kind described having at its lower end, a plurality of downwardly convergent receptacles arranged substantially in a common plane and covering substantially the entire plan area of the chamber, each such receptacle being provided at its lower end with a discharge opening.

Thus by increasing the number and thereby decreasing the "sizeof the individual receptacles, the depth thereof is correspondingly decreased, while maintaining the necessary slope or inclination of the sides thereof. Consequently, the depth of the collecting zone may be reduced to as little as a few inches thereby in the case of a slot blasting chamber, for example, avoiding on the one hand the necessity for making a large excavation, and on the other hand, the necessity for elevating the floor to an undesirable extentl Similarly 'in the case of a storage chamher the storage capacity may be increased.

The material discharged from the collecting receptacles is conveyed laterally in any convenient manner and preferably pneumatically, for which purpose the said dis charge openings of the receptacles communicate with a plurality of suitable tairducts, each of which is common to a plurality of'the saidreceptacles.

'The said air ducts maybe uniform in area throughout their length but for somepurposes the area thereof preferably increases progressively towards their discharge ends United States Patent ice 2 so that the velocity of the air therein is substantialy uniform as hereafter further explained.

The dimensions and shape of the air ducts are such as to ensure that they cannot become choked. by the abrasive, dust and debris or other particulate material which gravitates thereinto from any of the receptacles.

The said collecting receptacles may be of any convenient shape in plan and may be formed in any suitable manner and an important feature of the preferred embodiment of the invention resides in forming a collecting floor from a plurality of separate units each of a size and weight which may be conveniently handled and assembled in side-by-side relationship and which likewise may be readily transferred to another site if required. Each of the said units may comprise a single receptacle or a of rows disposed side by side.

Alternatively the receptacles may be formed by subdividing a plurality of parallel troughs formed by spaced parallel members. i

The said air ducts may be formed separately from the receptacles and may themselves comprise a plurality of separate units or each receptacle may be formed integrally with a corresponding section of the respective air duct.

irrespective of the manner in which the receptacles are constructed the upper edges of the sloping inner surfaces thereof are disposed as close as possible to the cor responding upper edges of the receptacles adjacent thereto so as to preclude the lodgrnent and accumulation of material on the upper ends of the receptacles. Otherwise expressed the aggregate area of the open upper ends of the receptacles is approximately equal to the floor area covered thereby.

In the drawings:

Figure l is a broken away and somewhat diagrammatic perspective view of a shot blasting chamber provided with a multiple hopper floor according to the invention,

Figure 2 is a view in sectional elevation of the hopper floor,

Figure 3 is a view in plan of the floor with portions broken away,

Figure 4 is a view in sectional elevation taken on the line 44 of Figure 3,

Figure 5 is a view in sectional elevation taken on the line 5-5 of Figure 3,

Figure 6 is a view similar to Figure 5 and shows a modified construction,

Figure 7 is a perspective view of another modification, and

Figure 8 is a diagrammatic view showing the invention applied to the floor of a storage chamber.

The slot blasting chamber shown in Figure l is rec tangular in shape and comprises a floor 10, opposite end walls 11 and 12, side walls 13 and a roof 14 to which a pipe 15 is connectedfor the supply of ventilating air to the interior of the chamber.

. The floor 10 supports a composite false floor comprising a large number of small square collecting hoppers 16 and 16 which cover the entire floor area and which are arranged in parallel rows extending lengthwise of the chamber between the end walls 11 and 12, the construcplate 19 by which the floor 10 is covered. The discharge ends of the several ducts 17 communicate adjacent to the end wall 12 with the inclined lower end 20 of a common take-oft duct 20 which in the illustrated construction covers the wall 12 and communicates at'its upper end with a pipe 21 arranged above the chamber. As it is necessary for the velocity of the air through the duct to be sulficiently high to maintain in suspension the abrasive particles, dust and the like, the duct is necessarily of very narrow thickness.

It will, however, be evident that the take-off duct 20 may be arranged in any convenient manner and one alternative arrangement is diagrammatically shown in Figure 8.

The hoppers 16 are formed above the ductforrning channel members 18, by supporting thereon a plurality of longitudinally extending sheet metal members 22 of right angle shape in cross-section. More particularly each of these members 22 is arranged with the free edges of its flanges resting on the central portions of an adjacent pair of duct-forming members 13 and is thus of inverted V shape in cross-section as shown in Figures 4 and 5. Consequently the adjacent sides of each adjacent pair of angle members 22 define an intervening V-shaped trough 23 which extends for substantially the full length of the chamber and is located directly above the respective duct 17.

Each V trough 23 is subdivided, by a plurality of regularly spaced and transversely disposed dividers 24, into the respective row of collecting hoppers 16 and 16 each divider (one of which is shown in a raised position in Figure 4), comprising a sheet metal strip of the same crosssectional shape as the members 22.

The top of the respective duct-forming member 18 is formed below and in register with each hopper 16 with a hole through which air and solid particles may pass into the respective duct 17.

It will be noted that the upper ends of the sloping inner surfaces of adjacent hoppers merge together so as to reduce to the minimum the areas on which grit may lodge without passing into the hoppers.

A fioor grille on which the work and the operators are supported, rests on top of the collecting hoppers 16 and 16*.

Those hoppers, designated 16 which are arranged in contact with the end wall 11 are connected to the respective ducts 1'7 by vertical discharge passages 26 of relatively large cross-sectional area whereby a larger volume of air will pass into the inlet end of each duct 17 than will pass thereinto through any of the remaining hoppers 16.

More particularly in the case of a shot blasting chamber, it is preferred that about two-thirds of the total volume of air should enter each duct through the respective hopper 16 and that the remaining one-third should enter the duct through the several remaining hoppers 16 though the relative rates of air flow may be varied according to requirements.

Also it is preferred to maintain a substantially constant rate of flow of air through each duct 17 for which purpose the Width thereof progressively increases towards the discharge end While the height thereof remains constant, as shown in Figures 1 and 2.

When, as in the illustrated construction, the longitu dinally extending members 22 and the dividers 24 are of right angle shape in cross-section, the sides of the hoppers 16 and 16 formed thereby are inclined at an angle of 45 to the horizontal plane, but it will be apparent that any other required angle of slope is obtainable, it being understood that the angle of slope should exceed the angle of repose of the particular material to be handled.

The plan dimensions and shape of the hoppers 16 and 16 may also be varied considerably according to requirements. For general purposes the upper ends of these hoppers may conveniently be about six inches square, in which case the depth of the hoppers is three inches when the angle-of slope 45 so that the total depthof the false floor, may be less than six inches irrespective of the width or. length of the chamber.

While the ducts 17 may be of other than rectangular shape in cross-section, they are necessarily of such a croso sectional shape that they cannot become choked by the material which may gravitate therethrough when the flow ot' ventilating air is cut off. In this regard it will be evident that if the grit or other like material is poured into a hopper 16, when the supply of air is cut off, it will form in the duct 17 a conical pile 31 having its sides sloping at the angle of repose of the material. When this pile builds up sufficiently it closes the respective discharge opening in the hopper at which time free air spaces of substantial area remain in the duct at the sides of the pile 31 (see Fig. 4) because the width of even the narrow portions of the duct 17 is so much greater than its height.

In use the air discharged by the blast guns (not shown) and supplemented usually by a considerably larger volume of air supplied to the chamber through the ventilating pipe 15, passes downwardly within the chamber and through the grille floor 30 and the collecting hoppers 16 and 16 into the longitudinally extending ducts 17. As previously explained the major portion of this air enters these ducts through the collecting hoppers 16 while the remainder is equally distributed among the much larger number of hoppers 16. The air may be supplied to the chamber under pressure, or alternatively or in addition the take-off ducts may be maintained under a reduced pressure by a suction fan as shown, for example, in Figure 8.

The spent abrasive, dust and debris passes with the air into the hoppers and ducts and is thus pneumatically conveyed to a storage hopper (not shown) it being understood that the velocity of the air in the ducts 17 and 21 is suificiently high for this purpose.

Due to the very large volume of air which is circulated through the chamber, as above described, the chamber is particularly well ventilated, while the high velocity of the air flow ensures that the corners and other parts of the chamber are swept free of dust and other solid particles.

For example, ventilating air may be supplied to the chamber of Figure 1 at the rate of cubic feet per minute per square foot of floor area. Thus if the chamber were 76" long the amount of air supplied would be 600 cubic feet per minute per foot of width so that if the collecting hoppers 16 and 16 were six inches square at the top, the flow of air through the discharge end of each duct 17 would be at the rate of 300 cubic feet per minute, there being two such ducts per foot of width of the chamber. If two-thirds of the air enters the duct 17 through the hoppers 16 then 200 cubic feet per minute pass through each hopper 16 while cubic feet per minute pass through the several hoppers 16 which communicate with the same duct, the sizes of the discharge openings in the hoppersbeing such as to provide the required distribution.

Consequently in order to maintain a substantially uniform rate of flow of air through the ducts 17 the latter if six inches wide at their discharge ends would be four inches wide at their "opposite or inlet ends where the hoppers 16 are located.

If desired the necessity for providing special hoppers as 16 with large area discharge passages 26 may be obviated by providing alternative inlet openings for the required volume of air. Thus as shown in broken lines at 17 at the left of Figure 2, the inlet ends of the ducts 17 may be extended upwardly above the level of the false floor, the open upper ends of these duct extensions being covered if desired by an inclined deflector plate 40.

It will be evident that the hopper floor may be constructed in various alternative ways. Thus in Figure 6 the ducts 17 are formed by channel section members 18 arranged with their flanges projecting upwardly and closed at the top by a metal'plate 34 in which the hopper discharge openings 25 are formed at the requisite positions. The hoppers 16 and 16 are formed above the plate 34, as in the construction previously described, by

Figure 7 shows another modification wherein each:

hopper 16 (or 16 is formed as an individual unit and is integral with the respective section of the corresponding duct 17 Thus a floor of any size may be completely covered by the requisite number of combined hopper and duct units arranged in parallel rows as in the preceding examples. It will be evident that if desired several of the said hopper units for the same or adjacent rows thereof may be formed integrally so that a reduced number of separate units are necessary to cover the floor. The hoppers 16 and 16 are of course not necessarily of square shape in plan.

The invention is also applicable to storage chambers for grain or other granular material, powder or the like. One example is shown diagrammatically in Figure 8 in which the chamber 35 is provided with a false floor comprising a large number of small hoppers 16 which together cover the total area of the floor .as in the shot blasting chamber previously described. The hoppers of each row similarly deliver into a corresponding duct 17 though the inlet ends 17 of the latter are, in this case, extended through the wall of the chamber and are open to the outside atmosphere. The common take-oil duct 21 to which the discharge ends of the several ducts 17 are connected, is in turn connected to a cyclone separator 36 from which the air may be withdrawn by a fan 38.

Thus normally a pile of the stored granular material is located in the respective duct 17 below each hopper 16 in the manner indicated in Figure 4. Each such pile thus prevents further discharge of the material through the respective hopper, but the piles do not block the ducts for the reason previously explained. When it is desired to remove material from the chamber, the fan 37 is operated to induce a flow of air through each duct 17 so that the material is progressively pneumatically conveyed to and deposited in the cyclone.

Figure 8 also shows in broken lines the usual hopper shape of the lower end of the storage chamber and thus indicates the considerable reduction of height made possible by the present invention.

In addition the composite collector floor may readily be installed in any suitable chamber and may likewise be removed if desired.

I claim:

1. In a chamber of the kind described, a substantially horizontal collector floor comprising a large number of relatively small downwardly convergent receptacles of hopper-like form arranged side-by-side in closely spaced relationship and having their upper ends communicating freely with the interior of the chamber, the aggregate area of the open upper ends of the receptacles being not substantially less than the area of the floor occupied by the receptacles, the said receptacles being arranged in parallel rows disposed side by side, means forming below each said row a corresponding laterally extending pneumatic discharge duct, each of the said receptacles having, at its lower end, a discharge opening which communicates freely with the respective duct, and air inlet means freely connecting the interior of the chamber to that end portion of each duct which is remote from the discharge end thereof, the cross-sectional area of such air inlet means being so related to the aggregate area of the discharge openings of the intervening receptacles in the respective row thereof, that a relatively large proportion of the total volume of air enters the duct through the said air inlet means.

2. A substantially horizontal collector floor for a shot-blasting chamber and the like, comprising a large number of relatively small downwardly convergent receptacles of hopper-like form, the said hoppers being arranged side by side and communicating freely with the interior of the chamber, the aggregate areaof the openings in the upper ends of the receptacles being not substantially less than the area of the floor occupied by 6 the receptacles, the said receptacles being arranged in parallel rows disposed side by side and means forming below each row a corresponding laterally extending pneumatic discharge duct of shallow depth, each of the said receptacles being provided at its reduced lower end with a discharge opening which communicates freely with the respective duct and the discharge opening of at least one of said receptacles, disposed adjacent that end of each duct which is remote from the discharge end thereof, being of substantially larger cross-sectional area than the discharge opening of each of the intervening receptacles in the said row whereby a relatively large proportion of the total air enters each duct adjacent to the said remote end.

3. A chamber of the kind described according to claim 1 wherein the said inlet means communicates with the interior of the chamber above the level of the said receptacles.

4. A shot-blasting chamber or the like comprising vertical walls, a ceiling having an air inlet opening therein; a floor; a false bottom a short distance above said floor, comprising a grille, a series of rows of small hoppers below the grille, said hoppers being placed closely together to occupy substantially the entire floor area, and having outlet openings at their lower end, and a series of collection ducts above said floor and below said hoppers, into which said hoppers empty; a main outlet duct into which said collection ducts empty adjacent one wall; and air inlet means into said collection ducts adjacent the opposite wall, said air inlet means having an area greater than the total area of all the hopper discharge openings.

5. The chamber of claim 4 wherein said collection ducts increase in width, while remaining constant in height, thereby increasing in cross-sectional area between said air inlet means and said main outlet duct, at a rate corresponding to the increased area afforded by their hopper discharge means.

6. A floor for shot blasting chambers and the like adapted to be supported upon an existing floor and entirely above ground level, said floor comprising a large number of hopper-type receptacles arranged in checkerboard formation, said receptacles consisting of square, separate hopper units each of a size and weight such that they may be conveniently handled and assembled in side by side relationship and readily transferred from one site to another, each hopper-unit comprising an inverted truncated, pyramidal shell open at its upper and lower ends, and conveying means for receiving from said hopper-units the material deposited therein and conducting said material away.

7. A composite false floor supported upon an existing floor entirely above ground level, said composite floor being of wafile design and consisting of a large plurality of small shallow hoppers, the walls of each hopper'merging downwardly toward a discharge opening at its lower end that is small in comparison with the area at the upper end of said hopper, and conveying means for receiving from said hoppers the material deposited therein and conducting said material away.

8. The structure as set forth in claim 7 in which substantially the entire false floor area is constituted .by miniature hopper-type receptacles arranged close together so that the floor as a whole has a checkerboard or waffle design, each hopper-type receptacle comprising an inverted truncated pyramidal shell open at its upper and lower ends, so that the leading edges of said hopper-type receptacles abut and present narrow ridges of inconsiderable area whereby material deposited upon the floor cannot accumulate, and duct means for receiving from said hopper-type receptacles the material deposited therein and conducting said material away.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS 8 Moore Apr. 5, 1932 Marx Sept. 26, 1944 Allerdice June 17, 1947 Polk July 18, 1950 Talmey Nov. 23, 1954 Liskey Apr. 17, 1956 

